The present invention relates to a cooler arrangement in a vehicle engine for air and/or gas into a combustion engine of the vehicle.
Particularly in heavy vehicles, the cooling system for cooling the combustion engine is increasingly being used for cooling other components and systems of the vehicle. If the cooling system is too heavily loaded, however, there is risk of its not coping satisfactorily with its main function of cooling the combustion engine.
The technique called EGR (exhaust gas recirculation) is a known way of leading part of the exhaust gases from a combustion process in a combustion engine back, via a return line, to an inlet line for supply of air to the combustion engine. A mixture of air and exhaust gases is thus supplied via the inlet line to the cylinders of the engine in which the combustion takes place. Adding exhaust gases to the air causes a lower combustion temperature, resulting inter alia in a reduced content of nitrogen oxides NOx in the exhaust gases. This technique is used for both Otto engines and diesel engines. However, the exhaust gases are at a relatively high temperature and have therefore to be cooled before they are led, together with the air, into the combustion spaces of the combustion engine. Conventional EGR coolers use the coolant of the vehicle's ordinary cooling system for cooling the recirculating exhaust gases.
The air led to a combustion engine is usually compressed to enable as large an amount of air as possible to be led into the combustion engine. The air undergoes heating during the compression. For an optimum amount of air to be supplied to the combustion engine, the compressed air has therefore to be cooled before it is led to the combustion engine. The compressed air is usually cooled in a charge air cooler which has air at the temperature of the surroundings flowing through it. The compressed air can thus be cooled to a temperature only a few degrees above the temperature of the surroundings. To achieve such cooling, the charge air cooler is usually situated in front of the ordinary radiator which cools the coolant. The coolant in the ordinary cooling system therefore undergoes less effective cooling when it is cooled by air which is at a higher temperature than the surroundings. The capacity of the ordinary cooling system is thus reduced when such a charge air cooler is used.